Bandwidth-based configuration of measurement gaps

ABSTRACT

Method and apparatus for improving the quality of measurements performed on non-serving frequencies and/or the quality of serving cell data reception by intelligently configuring measurement gaps during which a wireless device is to perform those measurements. The intelligent configuration processing entails obtaining information that identifies, for each of a plurality of candidate non-serving frequencies, one or more measurement bandwidths over which one or more corresponding measurements on that non-serving frequency are to be performed. In at least some embodiments, such candidate non-serving frequencies represent frequencies for which the device has requested measurements gaps. The processing further includes selecting a subset of the candidate non-serving frequencies based on the measurement bandwidths. The processing finally includes configuring measurement gaps during which the wireless device is to perform one or more measurements on the selected non-serving frequencies.

This application is a continuation of U.S. application Ser. No.13/979,905, filed 16 Jul. 2013, which was the National Stage ofInternational Application PCT/SE2012/050021, filed 12 Jan. 2012, whichclaims the benefit of U.S. Provisional Application No. 61/443,120, filed15 Feb. 2011, the disclosures of all of which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention generally relates to measurements of cells in awireless communication system, and particularly relates to configuringmeasurement gaps during which the device is to perform measurements ofcells on non-serving frequencies.

BACKGROUND

The availability of several techniques and devices for identifying thegeographical location of mobile device users has enabled a large varietyof commercial and non-commercial services, such as navigationassistance, enhanced social networking, location-aware advertising, andlocation-aware emergency calls. However, different services may havedifferent positioning accuracy requirements imposed by the application.In addition, some regulatory requirements on the positioning accuracyfor basic emergency services exist in some countries, such as the FCC'sE-911-related requirements in the United States.

In many environments, the position of a mobile device user can beaccurately estimated by using positioning methods based on GPS (GlobalPositioning System) or other satellite-based system. Nowadays, wirelessnetworks are often able to provide positioning-related assistance tomobile terminals (often referred to as user equipment, or UEs, orwireless terminals, mobile stations, or simply “mobiles”) to improve theterminal's receiver sensitivity and GPS start-up performance. Several ofthese techniques are known as Assisted-GPS positioning, or A-GPS.

GPS or A-GPS receivers may not be available in all UE, however.Furthermore, GPS is known to fail in certain indoor environments and inurban “canyons” in the radio shadows caused by tall buildings.Complementary terrestrial positioning methods, such as one approachcalled Observed Time-Difference-of-Arrival (OTDOA), have therefore beenstandardized by the 3rd-Generation Partnership Project (3GPP) and aredeployed in various wireless networks. In addition to OTDOA, the 3GPPstandards for the so-called Long-Term Evolution (LTE) wireless systemalso specify methods, procedures and signaling support for techniquescalled Enhanced Cell ID (E-CID) and Assisted Global Navigation SatelliteSystem (A-GNSS). Later, a network-based technique called UplinkTime-Difference-of-Arrival (UTDOA) may also be standardized for LTE.

Three key network elements for providing location services (LCS) in anLTE positioning architecture include the LCS Client, the LCS target andthe LCS Server. The LCS Server is a physical or logical entity managingpositioning for a LCS target device by collecting measurements and otherlocation information, assisting the terminal in measurements whennecessary, and estimating the LCS target location. A LCS Client is asoftware and/or hardware entity that interacts with a LCS Server for thepurpose of obtaining location information for one or more LCS targets,i.e. the entities being positioned. LCS Clients may reside in the LCStargets themselves. An LCS Client sends a request to LCS Server toobtain location information, and LCS Server processes and serves thereceived requests and sends the positioning result and optionally avelocity estimate to the LCS Client.

Position calculation can be conducted, for example, by a UE or by apositioning server, such as an Enhanced Serving Mobile Location Center,E-SMLC, or Secure User Plan Location (SUPL) Location Platform (SLP) inLTE. The former approach corresponds to the UE-based positioning mode,whilst the latter corresponds to the UE-assisted positioning mode.

Two positioning protocols operating via the radio network exist in LTE,LTE Positioning Protocol (LPP) and LPP Annex (LPPa) . . . . The LPP is apoint-to-point protocol between a LCS Server and a LCS target device,used in order to position the target device. LPP can be used both in theuser and control plane, and multiple LPP procedures are allowed inseries and/or in parallel thereby reducing latency. LPPa is a protocolbetween evolved Node B (eNodeB) and LCS Server specified only forcontrol-plane positioning procedures, although it still can assistuser-plane positioning by querying eNodeBs for information and eNodeBmeasurements. SUPL protocol is used as a transport for LPP in the userplane. LPP has also a possibility to convey LPP extension messagesinside LPP messages, e.g. currently Open Mobile Alliance (OMA) LPPextensions are being specified (LPPe) to allow e.g. foroperator-specific assistance data or assistance data that cannot beprovided with LPP or to support other position reporting formats or newpositioning methods.

A high-level architecture of such an LTE system 10 is illustrated inFIG. 1. In FIG. 1, the system 10 includes a UE 12, a radio accessnetwork (RAN) 14, and a core network 16. The UE 12 comprises the LCStarget. The core network 16 includes an E-SMLC 18 and/or an SLP 20,either of which may comprise the LCS Server. The control planepositioning protocols with the E-SMLC 14 as the terminating pointinclude LPP, LPPa, and LCS-AP. The user plane positioning protocols withthe SLP 16 as the terminating point include SUPL/LPP and SUPL. Althoughnote shown, the SLP 20 may comprise two components, a SUPL PositioningCenter (SPC) and a SUPL Location Center (SLC), which may also reside indifferent nodes. In an example implementation, the SPC has a proprietaryinterface with E-SMLC, and an Llp interface with the SLC. The SLC partof the SLP communicates with a P-GW (PDN-Gateway) 22 and an External LCSClient 24.

Additional positioning architecture elements may also be deployed tofurther enhance performance of specific positioning methods. Forexample, deploying radio beacons 26 is a cost-efficient solution whichmay significantly improve positioning performance indoors and alsooutdoors by allowing more accurate positioning, for example, withproximity location techniques.

To meet varying demands for different Location-Based Services (LBS), anLTE network will deploy a range of complementing methods characterizedby different performance in different environments. Depending on wherethe measurements are conducted and where the final position iscalculated, the methods can be UE-based, UE-assisted, or network-based,each with own advantages. The following methods are available in the LTEstandard for both the control plane and the user plane: (1) Cell ID(CID), (2) UE-assisted and network-based E-CID, including network-basedangle of arrival (AoA), (3) UE-based and UE-assisted A-GNSS (includingA-GPS), and (4) UE-assisted OTDOA.

Several other techniques such as hybrid positioning, fingerprintingpositioning and adaptive E-CID (AECID) do not require additionalstandardization and are therefore also possible with LTE. Furthermore,there may also be UE-based versions of the methods above, e.g. UE-basedGNSS (e.g. GPS) or UE-based OTDOA, etc. There may also be somealternative positioning methods such as proximity based location. UTDOAmay also be standardized in a later LTE release, since it is currentlyunder discussion in 3GPP.

Similar methods, which may have different names, also exist forradio-access technologies (RATs) other than LTE, such as CDMA, WCDMA orGSM.

With particular regard to the OTDOA positioning method, this methodmakes use of the measured timing of downlink signals received frommultiple base stations (evolved NodeBs, or eNodeBs, in LTE) at the UE.The UE measures the timing of the received signals using assistance datareceived from the LCS server, and the resulting measurements are used tolocate the UE in relation to the neighboring eNodeBs.

More specifically, the UE measures the timing differences for downlinkreference signals received from multiple distinct locations orneighboring cells. For each (measured) neighbor cell, the UE measuresReference Signal Time Difference (RSTD), which is a relative timingdifference between the neighbor cell and a defined reference cell. TheUE position estimate is then found as the intersection of hyperbolascorresponding to the measured RSTDs. At least three measurements fromgeographically dispersed base stations with a good geometry are neededto solve for two coordinates of the UE and the receiver clock bias. Inorder to solve for position, precise knowledge of the transmitterlocations and transmit timing offset is needed.

To enable positioning in LTE and facilitate positioning measurements ofa proper quality and for a sufficient number of distinct locations, newphysical signals dedicated for positioning (positioning referencesignals, or PRS) have been introduced and low-interference positioningsubframes have been specified in 3GPP. Details are specified in 3GPP TS36.211; as of February 2011, version 10.0.0 of this specification isavailable from http://www.3gpp.org.

PRS are transmitted from one antenna port of a base station according toa pre-defined pattern. A frequency shift, which is a function ofPhysical Cell Identity (PCI), can be applied to the specified PRSpatterns to generate orthogonal patterns. The mapping of frequencyshifts to PCT models an effective frequency reuse of six, which makes itpossible to significantly reduce neighbor cell interference on themeasured PRS and thus improve positioning measurements. Even though PRShave been specifically designed for positioning measurements and ingeneral are characterized by better signal quality than other referencesignals, the standard does not mandate using PRS. Other referencesignals, e.g. cell-specific reference signals (CRS) could be used forpositioning measurements, in principle.

PRS are transmitted in pre-defined positioning sub-frames grouped byseveral consecutive sub-frames (N_(PRS)), i.e., one positioningoccasion. Positioning occasions occur periodically with a certainperiodicity of N subframes, i.e. the time interval between twopositioning occasions. The standardized periods N are 160, 320, 640, and1280 ms, and the number of consecutive subframes may be 1, 2, 4, or 6[3GPP TS 36.211]. PRS configuration and PRS offset from System FrameNumber 0 (SFN0) are determined by a PRS configuration index defined in[3GPP 36.211] and signaled in the OTDOA assistance data. The number ofconsecutive DL subframes and the PRS bandwidth (which may be smallerthan the system bandwidth) may also be signaled in the OTDOA assistancedata. Of course, signaling the PRS bandwidth in the assistance data isonly useful if RSTD measurements are performed on PRS (as opposed toother reference signals).

PRS may also be muted, e.g., not transmitted. The positioning nodeinforms the UE about whether PRS is muted or not, e.g., by signaling acell-specific muting pattern which indicates PRS positioning occasionsin which the UE is expected to perform measurements for thecorresponding cell.

Information about such PRS and other information that will assist withpositioning measurements is included in so-called assistance data.Different sets of assistance data are typically used for differentmethods. Regardless, the positioning assistance data is sent by thepositioning server, or via some other node, to UEs or other radio nodesin order to assist with positioning measurements. For example,assistance data may be sent via LPP to an eNodeB for transmission to theUE. In this case, the transmission of assistance data may be transparentto the eNodeB and the Mobility Management Entity (MME). The assistancedata may also be sent by the eNodeB via LPPa to a positioning server forfurther transfer to the UE. In some cases, the assistance data may besent on request from a wireless device that needs to performmeasurements. In other cases, the assistance data is sent in anunsolicited way.

Since for OTDOA positioning PRS signals from multiple distinct locationsneed to be measured, the UE receiver may have to deal with PRS that aremuch weaker than those received from the serving cell. Furthermore,without an approximate knowledge of when the measured signals areexpected to arrive in time and what is the exact PRS pattern, the UEmust perform signal search within a large window. This can impact thetime and accuracy of the measurements as well as the UE complexity. Tofacilitate UE measurements, the network transmits assistance data to theUE, which includes, among other things, reference cell information, aneighbor cell list containing Physical Cell Identifiers (PCIs) ofneighbor cells, the number of consecutive downlink subframes within apositioning occasion, PRS transmission bandwidth, frequency, etc.

In LPP, the OTDOA assistance data is provided within the InformationElement (IE) OTDOA-ProvideAssistanceData, as shown in FIG. 2. Similarstructures for OTDOA exist in LPPe.

The OTDOA assistance data includes information about the reference celland neighbor cells for which OTDOA is to be determined. The neighborcells may or may not be on the same frequency as the reference cell, andthe reference cell may or may not be on the same frequency as theserving cell, and may or may not be the serving cell. Measurements thatinvolve cells on a frequency different than the serving cell areinter-frequency measurements. Measurements on the same frequency as theserving cell are intra-frequency measurements. Different requirementsapply for intra- and inter-frequency measurements.

Note that assistance data delivery is not required for UE- oreNodeB-assisted forms of E-CID positioning and this is not currentlysupported without EPDU elements. UE-based E-CID location is notcurrently supported, and the assistance data delivery procedure is notapplicable to uplink E-CID positioning. No assistance data is currentlyspecified for E-CID for LPP. Some assistance data, however, may beprovided for E-CID e.g. via LPPe.

In this regard, with Open Mobile Alliance (OMA) LPP extension (LPPe),assistance data is enhanced with the possibility to assist a largerrange of positioning methods (e.g. assistance data may also be providedfor E-CID or other methods of other RATs, e.g. OTDOA UTRA or E-OTD GSM,or other PLMN networks). Furthermore, there is also a possibility ofcarrying over a black-box data container meant for carryingvendor-/operator-specific assistance data.

Also note that LTE specifications enable Frequency Division Duplex (FDD)and Time Division Duplex (TDD) operation modes. Additionally, halfduplex operation is also specified, which is essentially FDD operationmode but with transmission and receptions not occurring simultaneouslyas in TDD. Half duplex mode has advantages with some frequencyarrangements where the duplex filter may be unreasonable, resulting inhigh cost and high power consumption. Since carrier frequency number(EARFCN) is unique, by knowing it, it is possible to determine thefrequency band, which is either FDD or TDD. However, it may be moredifficult to find the difference between full duplex FDD and half-duplexFDD (HD-FDD) without explicit information since the same FDD band can beused as full FDD or HD-FDD.

Further, inter-frequency measurements may in principle be considered forany positioning method, even though currently not all measurements arespecified by the standard as intra- and inter-frequency measurements.When performing inter-frequency measurement, the serving and targetcarrier frequencies may belong to the same duplex mode or to differentduplex modes e.g. LTE FDD-FDD inter-frequency, LTE TDD-TDDinter-frequency, LTE FDD-TDD inter-frequency or LTE TDD-FDDinter-frequency scenario. The FDD carrier may operate in full duplex oreven in half duplex mode. Examples of inter-frequency measurementscurrently specified by the standard are Reference Signal Time Difference(RSTD) used for OTDOA, RSRP and RSRQ which may be used e.g. forfingerprinting or E-CID.

In LTE, measurement gaps are configured by the network to enableinter-frequency measurements on the other LTE frequencies. Themeasurements may be done for various purposes: mobility, positioning,self-organizing network (SON), minimization of drive tests, etc.Regardless, the gap configuration is signaled to the UE over the RadioResource Control (RRC) protocol as part of the measurementconfiguration. A UE that requires measurement gaps for positioningmeasurements, e.g., OTDOA, may send an indication to the network, e.g.eNodeB, upon which the network may configure the measurement gaps.Furthermore, the measurement gaps may need to be configured according toa certain rule, e.g. inter-frequency RSTD measurements for OTDOA requirethat the measurement gaps are configured according to theinter-frequency requirements in 36.133, Section 8.1.2.6, e.g. notoverlapping with PRS occasions of the serving carrier and using gappattern #0.

In LTE, inter-RAT measurements (e.g., measurements on other RATs likeUTRA, GSM, CDMA2000, etc.) are typically defined similar tointer-frequency measurements. Indeed, they may also require configuringmeasurement gaps like for inter-frequency measurements. Althoughinter-RAT measurements often have more relaxed requirements and havemore measurements restrictions, the same gap pattern is used for alltypes of inter-frequency and inter-RAT measurements. Therefore E-UTRANmust provide a single measurement gap pattern with constant gap durationfor concurrent monitoring (i.e. cell detection and measurements) of allfrequency layers and RATs.

As a special example of inter-RAT measurements there may also bemultiple networks, which use the overlapping sets of RATs. The examplesof inter-RAT measurements specified currently for LTE are UTRA FDD CPICHRSCP, UTRA FDD carrier RSSI, UTRA FDD CPICH Ec/No, GSM carrier RSSI, andCDMA2000 1×RTT Pilot Strength.

For positioning, assuming that LTE FDD and LTE TDD are treated asdifferent RATs, the current standard defines inter-RAT requirements onlyfor FDD-TDD and TDD-FDD measurements, and the requirements are differentin the two cases. There are no other inter-RAT measurements specifiedwithin any separate RAT for the purpose of positioning and which arepossible to report to the positioning node (e.g. E-SMLC in LTE).

It is mandatory for all UEs to support all intra-RAT measurements(including both inter-frequency and intra-band measurements) and meetthe associated requirements. However the inter-band and inter-RATmeasurements are UE capabilities, which are reported to the networkduring the call setup. The UE supporting certain inter-RAT measurementsshould meet the corresponding requirements. For example a UE supportingLTE and WCDMA should support intra-LTE measurements, intra-WCDMAmeasurements and inter-RAT measurements (i.e. measuring WCDMA whenserving cell is LTE and measuring LTE when serving cell is WCDMA). Hencenetwork can use these capabilities according to its strategy. Thesecapabilities are highly driven by factors such as market demand, cost,typical network deployment scenarios, frequency allocation, etc.

Notably, in single carrier LTE, a cell may operate at channel bandwidthsranging from 1.4 MHz to 20 MHz. However, a single-carrier legacy UEshall be able to receive and transmit over 20 MHz, i.e., the maximumsingle-carrier LTE bandwidth. If the serving-cell bandwidth is smallerthan 20 MHz, then the UE shortens the bandwidth of its radio frequency(RF) front end. For example, if the serving-cell bandwidth (BW) is 5MHz, then the UE will likewise configure its RF BW to 5 MHz. Thisapproach has several advantages. For example, it enables the UE to avoidnoise outside the current reception bandwidth, and it saves UE batterylife by lowering power consumption.

However, such reconfiguration of the UE reception and/or transmissionbandwidth involves some delay, e.g., 0.5-2 ms, depending on UEimplementation and also on whether both UL BW and DL BW are reconfiguredat the same time or not. This small delay is often referred to as‘glitch’. During the glitch the UE cannot receive from the serving cellor transmit to the serving cell. Hence this may lead to interruption indata reception or transmission from or to the serving cell. The UE isalso unable to perform any type of measurements during the glitch. Theglitch occurs either when the UE extends its bandwidth (e.g. from 5 MHzto 10 MHz) or when it shortens its bandwidth (e.g. from 10 MHz to 5MHz).

Furthermore, when the UE operates at a bandwidth lower than its maximumreception capability and the UE then wants to measure over a largerbandwidth, it has to open its receiver for performing the measurement.Thus, in this case (i.e. when current BW<max BW) the glitch occursbefore and after the UE obtains each measurement sample, if the UEreconfigures back to its current operation after each measurement sampleover the larger bandwidth.

The glitch also occurs when a UE capable of carrier aggregation (CA)reconfigures its bandwidth from single carrier to multiple carrier modeor vice versa. For example consider a UE that is capable of CA and thatsupports 2 downlink (DL) component carriers (CCs), each of 20 MHz,including a primary CC (PCC) and a secondary CC (SCC). If the secondarycomponent carrier is deactivated by the serving/primary cell then the UEwill shorten its BW e.g. from 40 MHz to 20 MHz. This may cause 1-2 msinterruption on the PCC.

According to current standards, the maximum allowed measurementbandwidth on a carrier frequency is defined by the parameterTransmission Bandwidth Configuration “N_(RB)” in 3GPP TS 36.104, whichmay take values of 6, 15, 25, 50, 75 and 100 resource blocks. The DLbandwidth information of a cell is signaled in the Mater InformationBlock (MIB) which the UE reads before it can camp on the cell; the ULbandwidth information, if different from the DL bandwidth information,may further be signaled in SystemInformationBlockType2 (SIB2) [3GPP TS36.331].

For cell reselection, i.e., when the UE has to measure on neighborcells, the cell re-selection parameters that are common forintra-frequency, inter-frequency and/or inter-RAT cell re-selection aresignaled in SystemInformationBlockType3 (SIB3). The elementintraFreqCellReselectionInfo of SIB3 contains the allowedMeasBandwidthelement, which corresponds to the DL bandwidth for measurements onintra-frequency cells. If that element is absent, the DL measurementbandwidth for intra-frequency cells is assumed to be the same as thatindicated by the dl-Bandwidth included in MIB. The allowed measurementbandwidth is not signaled per cell, since it is assumed to be the sameas for the serving cell, which is signaled in MIB and SIB2.

The information relevant for inter-frequency cell reselection only maybe signaled via SIB5, which includes cell re-selection parameters commonfor a frequency as well as cell specific re-selection parameters. Theallowed measurement bandwidth information is signaled per frequency inthe InterFreqCarrierFreqInfo element.

Thus, cell-specific bandwidth information currently is not provided forcell re-selection. Rather, bandwidth information for cell re-selectionis only provided per carrier.

Other cell-specific information for cell re-selection is currentlyprovided for intra-frequency cells or inter-frequency cells. Forintra-frequency cells, the information is provided in theIntraFreqNeighCellInfo element, when a list of cells is signaled inSIB4. For inter-frequency cells, the information is provided in theInterFreqNeighCellInfo element, when a list of cells is included inInterFreqCarrierFreqInfo signaled in SIB5.

Further, a neighCellConfig element is used to indicate whether or notsome configurations for a neighbor cell are the same as for the servingcell. This element with the current standard can be signaled as either apart of intraFreqCellReselectionInfo (in SIB3) or a part ofInterFreqCarrierFreqInfo (in SIB5).

Note that the neighCellConfig element is used to indicate potentialconfiguration differences among cells of a particular frequency, withoutcell details. Currently, the neighCellConfig element is used to provideonly the information related to MBSFN and TDD UL/DL configuration ofneighbor cells of such frequency. In particular, values for theneighCellConfig element include 00, 10, 01, and 11. A value of ‘00’indicates that not all neighbor cells have the same MBSFN subframeallocation as the serving cell on the frequency, if configured, and asthe PCell otherwise. A value of ‘10’ indicates that the MBSFN subframeallocations of all neighbor cells are identical to or subsets of that inthe serving cell on this frequency, if configured, and of that in thePCell otherwise. A value of ‘01’ indicates that no MBSFN subframes arepresent in all neighbor cells. Finally, a value of ‘11’ indicates thatthere is a different UL/DL allocation in neighboring cells for TDDcompared to the serving cell on this frequency, if configured, andcompared to the PCell otherwise. Note that, for TDD, 00, 10 and 01 areonly used for the same UL/DL allocation in neighboring cells compared tothe serving cell on this frequency, if configured, and compared to thePCell otherwise.

In view of the above described details, a UE may need to measurereference signals transmitted by multiple cells, e.g., for performingpositioning measurements. This proves problematic in certaincircumstances. One problematic circumstance occurs when the multiplecells have different cell bandwidths. Another problematic circumstanceoccurs when one or more of the cells do not use the full cell bandwidth,such as when those cells are provided by beacon devices. Still anotherproblematic circumstance occurs when the reference signals to bemeasured are transmitted in the multiple cells with different bandwidths(irrespective of the cell bandwidths of those cells). And yet anotherproblematic circumstance occurs when the UE obtains differentmeasurement bandwidth information for cells to be measured and therebymeasures those cells over different bandwidths.

In all of these circumstances, the UE has to reconfigure the receiver toenable measurements of cells with a larger bandwidth, which may benecessary to meet e.g. measurement accuracy requirements with respect tothose cells. This proves problematic because configuring a receiver to alarger bandwidth, to meet measurement accuracy requirements for cellswith that larger bandwidth, may degrade measurement quality in othercells with either a smaller associated measurement bandwidth or with asmaller cell bandwidth. Configuring the receiver to a larger bandwidthmay also prove problematic if that bandwidth is larger than theserving-cell bandwidth. Indeed, particularly where the measurementsbeing performed are intra-frequency measurements, measuring cells oversuch large bandwidth degrades the quality with which the UE receivesdata from the serving cell over a smaller bandwidth.

Still further, positioning measurements may be performed periodically.For instance, OTDOA positioning measurements are performed inpositioning subframes that occur in blocks of consecutive DL subframesand with periodicity of 160 ms, 320, 640 ms, or 1280 ms. Receiverreconfiguration to a new measurement bandwidth in certain subframestakes time, and reconfiguring it back to the normal-operationmeasurement bandwidth in normal subframes also takes time. Thisreconfiguration time reduces the total effective measurement time, whichtypically results in degraded measurement accuracy and/or data receptionquality.

Moreover, when the network (eNodeB in LTE) configures measurement gapsfor the UE to enable positioning measurements, there may also be somecells on inter-frequency(ies) or another RAT with a differenttransmission or measurement bandwidth of signals used for positioning.In some cases, e.g., when there are multiple frequencies and the signalsfor positioning occur at different time instances, the network (oreNodeB, in particular) may need to choose for which frequency themeasurement gaps are to be configured. Known approaches fail to make aselection in this regard that would improve measurement accuracy and/ordata reception quality.

SUMMARY

Embodiments herein advantageously improve the quality of measurementsperformed on non-serving frequencies and/or the quality of serving celldata reception by intelligently configuring measurement gaps duringwhich a wireless device is to perform those measurements. Suchintelligent configuration entails selecting only a subset of non-servingfrequencies for which to configure measurement gaps, based on thebandwidth over which the associated measurements are to be performed. Inat least some embodiments, the configuration further bases the selectionon the serving-cell bandwidth.

More particularly, embodiments herein include a method and apparatus forconfiguring measurement gaps during which a wireless device is toperform measurements of one or more neighbor cells on one or morenon-serving frequencies. Processing according to the method, inparticular, entails obtaining information that identifies, for each of aplurality of candidate non-serving frequencies, one or more measurementbandwidths over which one or more corresponding measurements on thatnon-serving frequency are to be performed. In at least some embodiments,such candidate non-serving frequencies represent frequencies for whichthe device has requested measurements gaps. Regardless, processingfurther includes selecting, based on the measurement bandwidths, asubset of the candidate non-serving frequencies. Processing finallyincludes configuring measurement gaps during which the wireless deviceis to perform one or more measurements on the selected non-servingfrequencies.

Thus, rather than configuring measurement gaps for all of the candidatenon-serving frequencies, the processing configures measurement gaps foronly a subset of one or more of those non-serving frequencies. And,notably, the processing does so intelligently based on informationobtained regarding the bandwidths over which the associated measurementsare to be performed.

In one or more embodiments, the subset of candidate non-servingfrequencies for which to configure measurement gaps is selected so as tomaximize the average bandwidth over which measurements will beperformed. Indeed, performing measurements over a larger bandwidth inthis way increases the quality and accuracy of those measurements.

In one or more other embodiments, the subset is advantageously selectedbased not only on the measurement bandwidths, but also on theserving-cell bandwidth, or more particularly based on the measurementbandwidths' relation to the serving-cell bandwidth. Such may entailpreferentially selecting for inclusion in the subset candidatenon-serving frequencies on which the most neighbor cells are to bemeasured over the serving-cell bandwidth. Or, this may entailpreferentially selecting for inclusion in the subset candidatenon-serving frequencies on which the most neighbor cells are to bemeasured over a bandwidth that does not exceed a defined threshold setbased on the serving-cell bandwidth.

Of course, the present invention is not limited to the above featuresand advantages. Indeed, those skilled in the art will recognizeadditional features and advantages upon reading the following detaileddescription, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates components of the LTE positioning architecture.

FIG. 2 illustrates the structure of the provideAssistanceData element inthe LPP protocol.

FIG. 3 is a block diagram of a wireless communication system thatincludes a radio network node configured according to one or moreembodiments herein.

FIG. 4 is a block diagram of a radio network node configured accordingto one or more embodiments.

FIG. 5 is a logic flow diagram of a method implemented by a radionetwork node for configuring measurement gaps during which a wirelessdevice is to perform measurements of one or more neighbor cells on oneor more non-serving frequencies, according to one or more embodiments.

DETAILED DESCRIPTION

FIG. 3 depicts a simplified example of wireless communication system 30according to one or more embodiments. As shown, the system 30 includes aRadio Access Network (RAN) 32, a Core Network (CN) 34, and one or morewireless devices 36. The RAN 32 and CN 36 enable a wireless device 36 toaccess one or more external networks 38, such as the Public SwitchedTelephone Network (PSTN) or the Internet.

The RAN 32 includes a number of base stations 40 that are geographicallydistributed across the wide geographic area served by the system 30.Each base station 40 provides radio coverage for one or more respectiveportions of that geographic area, referred to as cells 42. Because ofthis, a wireless device 36 may move within or between cells 42 and maycommunicate with one or more base stations 40 at any given position.

Different cells 42 may have different nominal sizes, depending on themaximum transmit power utilized by the base stations 40 serving thosecells 42. As shown, for example, base station 40-1 has a relativelylarge maximum transmit power and correspondingly serves wireless devices36 within a relatively large cell 42-1, while base station 40-5 has arelatively small maximum transmit power and correspondingly serveswireless devices 36 within a relatively small cell 40-5. In general,different base stations 40 that have different pre-defined maximumtransmit powers (and thereby serve cells 42 of different nominal sizes)belong to different base station classes (e.g., a macro base stationclass, a micro base station class, a pico base station class, etc.).

Furthermore, different cells 42 may generally be configured to operateover different predefined bandwidths, referred to herein as cellbandwidths. A given cell 42 may transmit a signal over a bandwidthsmaller than its cell bandwidth, but may not transmit a signal over abandwidth larger than its cell bandwidth.

Within this context, FIG. 3 depicts a particular wireless device 36that, at its current position, is served by base station 40-s in thesense that the device 36 receives data from that base station 40-s. Thebase station 40-s transmits this data to the device 36 on a particularfrequency (referred to as the serving-cell frequency) and over aparticular bandwidth (known as the serving-cell bandwidth). Thus, fromthe perspective of this wireless device 36, base station 40-s is theserving base station and cell 42-s is the serving cell. Other cells 42that are geographically adjacent to or partially coincident with theserving cell 42-s are appropriately referred to as neighboring cells. Inthis simplified example, all cells 42 shown are neighboring cells exceptfor cells 40-9 and 40-10.

Each of the cells 42 (via its base station 40) periodically transmits aso-called reference signal 44. A reference signal 44 as used herein is apredetermined signal that is known to both a cell 42 transmitting thatsignal and a wireless device 36 receiving the signal. Reference signals44 transmitted by the cells 42 in this way can be measured by a wirelessdevice 36. This process by which a device 36 measures reference signals44 transmitted by a cell 42 is also referred to herein, for convenience,as a device performing measurements of that cell 42.

Regardless, a reference signal 44 may be transmitted by a cell 42 on thesame or a different frequency as the serving-cell frequency. The device36 may measure reference signals 44 transmitted by neighbor cells 42 onthe serving-cell frequency at the same time as which the device 36receives data from the serving cell 42-s on that frequency. Suchmeasurements are appropriately referred to as intra-frequencymeasurements. Conversely, in at least some embodiments, the device 36must measure reference signals 44 transmitted by neighbor cells 42 on anon-serving frequency at a different time than the time at which thedevice 36 receives data from the serving cell 42-s on the servingfrequency. These measurements may generally be referred to herein asinter-frequency measurements, although the described embodiments areequally applicable to other measurements performed on non-servingfrequencies, such as inter-RAT measurements and inter-band measurements.In any case, these measurements can then be used for various purposes,including for example mobility management or determining the geographicposition of the device 36.

In this regard, a wireless device 36 may establish a session with aserver 46 in the core network 35 for accomplishing such a purpose. Thissession may include one or more transactions between the device 36 andthe server 46. Each transaction pertains to a particular operation, suchas the exchange of capabilities, the transfer of assistance data fromthe server 46 to the device 36 for assisting the device 36 to performmeasurements, or the transfer of information concerning the ultimatepurpose of those measurements (e.g., the actual position of the device36). Since the device 36 performs measurements in the context of such asession, the session will be referred to herein as a measurement sessionof the device 36.

Within any given measurement session of a device 36, the device 36 mayperform measurements of different cells 42, which may not only includeneighbor cells but also the serving cell. Any one of these cells 42 mayserve as a so-called reference cell in the context of the measurements.In this regard, measurements performed on the reference cell serve as areference for measurements performed on the other cells 42.

Of particular relevance, the device 36 performs measurements of neighborcells 42 on non-serving frequencies during so-called measurement gaps. Ameasurement gap as used herein refers to a period of time in which thewireless device 36 performs a measurement of a neighbor cell 42 on anon-serving frequency, and does not transmit any data or otherwisecommunicate with the serving cell 42-s or other cell 42 on theserving-cell frequency. Within any given measurement gap, the device 36can perform measurements on only a limited number of non-servingfrequencies (typically only one at a time).

To this end, the serving base station 40-s or some other radio networknode in the RAN 32 configures (i.e., times or otherwise schedules) oneor more measurement gaps during which the wireless device 36 is toperform such measurements on one or more non-serving frequencies.Notably, the base station 40-s does so intelligently, based oninformation obtained regarding the bandwidth(s) over which themeasurements are to be performed.

FIG. 4 illustrates additional details of such a radio network node inthis regard. As shown, a radio network node 50 includes one or morecommunication interfaces 52, a memory 54, and one or more processingcircuits 56. The one or more communication interfaces 52 may include anetwork interface for communicatively coupling the node 50 to othernodes in the RAN 32 or CN 34. The one or more communication interfaces52 may further include a radio interface for communicatively couplingthe node 50 to wireless devices 36.

The one or more processing circuits 56 configure the above-mentionedmeasurement gaps. In this regard, the one or more processing circuits 56may functionally include a gap configuration circuit 58. As explainedmore fully below, the gap configuration circuit 58 is configured toobtain information that identifies, for each of a plurality of candidatenon-serving frequencies, one or more measurement bandwidths over whichone or more corresponding measurements on that non-serving frequency areto be performed.

In at least some embodiments, such candidate non-serving frequenciesrepresent frequencies for which the device 36 has requested the radionetwork node 50 to configure measurements gaps. The gap configurationcircuit 58 may therefore receive a request from the device 36 thatidentifies the candidate non-serving frequencies and that requests thenode 50 to configure gaps for performing measurements on thoseidentified frequencies. In this case, the gap configuration circuit 58may obtain the above-mentioned measurement bandwidth information byretrieving that information from within the request received from thewireless device 36. Alternatively, the gap configuration circuit 58 mayobtain the measurement bandwidth information by, responsive to receivingthe gap configuration request from the device 36, requesting thatinformation from server 46 or some other network node in the corenetwork 35. Of course, other information about the cells on whichmeasurements are to be performed may be obtained in similar ways, suchas timing information regarding when the cells 42 are to transmit thereference signals 44 to be measured (e.g., a set of timing offsets,muting information, and the like).

In any case, the gap configuration circuit 58 next selects, based on themeasurement bandwidths, a subset of the candidate non-servingfrequencies. The gap configuration circuit 58 then configuresmeasurement gaps during which the wireless device 36 is to perform oneor more measurements on the selected non-serving frequencies. Thus,rather than configuring measurement gaps for all of the candidatenon-serving frequencies, the gap configuration circuit 58 configuresmeasurement gaps for only a subset of one or more of those non-servingfrequencies. And, notably, the gap configuration circuit 58 does sointelligently based on information obtained regarding the bandwidthsover which the associated measurements are to be performed.

In at least some embodiments, this configuration of measurement gaps foronly a subset of candidate non-serving frequencies is necessitatedbecause the gap configuration circuit 58 cannot configure gaps for allof those frequencies. Indeed, in these embodiments, measurement gaps aretimed according to a predetermined pattern. This predetermined patterncomprises a single, periodic measurement gap pattern that defines theparticular times at which a fixed number of gaps are to occur.Configuring measurement gaps thus entails specifying which candidatenon-serving frequencies are to be measured during which measurementgaps, with the limitation that only a certain number (e.g., one) ofnon-serving frequencies can be measured during any given gap. Based onthis limitation, the gap configuration circuit 58 in these embodimentsdetermines whether or not measurement gaps can be configured for all ofthe candidate non-serving frequencies using the gap pattern. If so, thegap configuration circuit 58 configures the gaps accordingly, But, ifnot, the gap configuration circuit 58 selects and configures the gapsfor a subset of candidate non-serving frequencies as described above.

Specifically, in one or more embodiments, the gap configuration circuit58 selects the subset of candidate non-serving frequencies for which toconfigure measurement gaps so as to maximize the average bandwidth overwhich measurements will be performed. Indeed, performing measurementsover a larger bandwidth in this way increases the quality and accuracyof those measurements.

In more detail, the gap configuration circuit 58 in these embodimentsdetermines a so-called majority measurement bandwidth for each candidatenon-serving frequency. A majority measurement bandwidth for a givencandidate non-serving frequency, as used herein, represents themeasurement bandwidth over which the majority of measurements on thatnon-serving frequency are to be performed. Having determined such amajority measurement bandwidth for each non-serving frequency, the gapconfiguration circuit 58 preferentially selects, for inclusion in thesubset, candidate non-serving frequencies that have the greatestmajority measurement bandwidth.

As a simplified example, assume that the gap configuration circuit 58receives a gap configuration request from a wireless device 36 thatidentifies the candidate non-serving frequencies as being F1, F2, andF3. If measurements are to be performed on F1 with respect to 4different cells (e.g., cells 40-1 through 40-4 in FIG. 1) overrespective measurement bandwidths of 5 MHz, 5 MHz, 5 MHz, and 15 MHz,the gap configuration circuit 58 determines the majority measurementbandwidth for F1 to be 5 MHz. Similarly, if measurements are to beperformed on F2 with respect to those same cells 40-1 through 40-4 overrespective measurement bandwidths of 5 MHz, 10 MHz, 10 MHz, and 10 MHz,the gap configuration circuit 58 determines the majority measurementbandwidth for F2 to be 10 MHz. Finally, if measurements are to beperformed on F3 with respect to the cells 40-1 through 40-4 overrespective measurement bandwidths of 10 MHz, 15 MHz, 15 MHz, and 15 MHz,the gap configuration circuit 58 determines the majority measurementbandwidth for F3 to be 15 MHz. Assuming the gap configuration circuit 58can only configure measurement gaps for a subset that includes 2 of the3 candidate non-serving frequencies F1, F2, and F3, the circuit 58preferentially selects frequencies F2 and F3 for inclusion in thesubset, because those frequencies have the greatest majority measurementbandwidths (i.e., 10 MHz and 15 MHz, as compared to 5 MHz for F1).

Note of course that there may be certain exceptions to the aboveselection process, e.g., to account for one or more requirementspertaining to measurement accuracy. For instance, some types ofmeasurements (e.g., for positioning) must be performed with respect toat least a defined minimum number of cells 42. In this case, even if aparticular non-serving frequency would have been selected for inclusionin the subset based on its majority measurement bandwidth, thatfrequency may nonetheless be excluded if measurements on the frequencycannot be performed with respect to at least the minimum number ofcells.

Note also that the above embodiments selected the subset of candidatenon-serving frequencies without regard to the serving-cell bandwidth.This is because the embodiments simply assume that, since the wirelessdevice 36 will not be receiving data from the serving cell 42-s duringthe configured measurement gaps, the quality of data reception will notbe affected by re-configuring the receiver during measurement gaps toperform measurements over a bandwidth larger than the serving-cellbandwidth (to thereby increase measurement quality). Other embodimentsherein, however, advantageously recognize that the quality of datareception and/or the quality of reference signal measurements may stillbe affected in this case, especially if measurements of the referencecell are to be performed on the serving-cell frequency (i.e., as anintra-frequency measurement).

Thus, according to one or more embodiments, the gap configurationcircuit 58 advantageously selects the subset also based on theserving-cell bandwidth, or more particularly based on the measurementbandwidths' relation to the serving-cell bandwidth. Of course, since theserving-cell bandwidth's impact is most pronounced when the referencecell transmits its reference signal on the serving-cell frequency,selection of the subset based on the serving-cell bandwidth may beconditional on that being the case. That is, in at least someembodiments, the gap configuration circuit 58 determines whether or notto select the subset also based on the serving-cell bandwidth, dependingon whether or not the reference cell is on the serving-cell frequency.

In any case, when the gap configuration circuit 58 does select thesubset based on the serving-cell bandwidth, the circuit 58 in someembodiments preferentially selects for inclusion in the subset candidatenon-serving frequencies on which the most neighbor cells are to bemeasured over the serving-cell bandwidth. In the context of the aboveexample, for instance, assume that the serving-cell bandwidth is 5 MHz.As such, the gap configuration circuit 58 determines that 3 neighborcells on F1 are to be measured over the 5 MHz serving-cell bandwidth, 1neighbor cell on F2 is to be measured over the 5 MHz serving-cellbandwidth, and no neighbor cells on F3 are to be measured over the 5 MHzserving-cell bandwidth. Accordingly, the gap configuration circuit 58preferentially selects F1 and F2 for inclusion in the subset, sincethose non-serving frequencies have more cells that are to be measuredover the serving-cell bandwidth than F3.

Other embodiments nonetheless recognize that at least some of theaforementioned advantages are realized if measurements are performedover a bandwidth that, although larger than the serving-cell bandwidth,is only larger by a defined threshold. In these embodiments, therefore,the gap configuration circuit 58 preferentially selects for inclusion inthe subset candidate non-serving frequencies on which the most neighborcells are to be measured over a bandwidth that does not exceed a definedthreshold set based on the serving-cell bandwidth. Such threshold may beset, for instance, to be larger than the serving-cell bandwidth. In someembodiments, the threshold is set in this way to be a defined offset(e.g., a 5 MHz offset) or ratio (e.g., 2) from the serving-cellbandwidth (where, if the offset is 0 MHz or the ratio is just 1, thisembodiment becomes equivalent in effect to the preceding embodiment).Again in the context of the above example, if the threshold is set to beeither a 5 MHz offset or a ratio of 2 above the 5 MHz serving-cellbandwidth, the gap configuration circuit 58 preferentially selects forinclusion in the subset candidate non-serving frequencies on which themost neighbor cells are to be measured over a bandwidth that does notexceed 10 MHz. In this case, therefore, the gap configuration circuit 58would again select F1 and F2 for inclusion in the subset, based on thefact that 3 cells on F1 and 4 cells on F2 are to be measured over lessthan a 10 MHz bandwidth, while only 1 cell on F3 is to be measured overless than a 10 MHz bandwidth.

Of course, rather than defining such a threshold explicitly in relationto the serving-cell bandwidth, the gap configuration circuit 58 may besimply configured with a defined maximum bandwidth that inherentlyembodies some relation to the serving-cell bandwidth. That is, in someembodiments, the gap configuration circuit 58 preferentially selects,for inclusion in the subset, candidate non-serving frequencies on whichthe most neighbor cells are to be measured over a measurement bandwidththat does not exceed a defined maximum bandwidth (e.g., 10 MHz). Suchembodiments prove to yield similar advantages to those just described,despite not defining the maximum bandwidth explicitly with respect tothe serving-cell bandwidth.

Those skilled in the art will readily appreciate that the examplesherein have been simplified in a number of respects for purposes ofillustration. Indeed, at least some aspects of the processingillustrated above may be performed as part of a larger set of supportingor complementary functions. In one embodiment, for instance, the radionetwork node 50 configures a measurement pattern for the wireless device36 to perform the one or more measurements, where this measurementpattern indicates low-interference subframes in which the wirelessdevice is to perform those measurements. Such a pattern may be forinstance a PRS configuration, PRS muting, or eICIC measurement patternin LTE embodiments.

Those skilled in the art will further understand that the measurementsat issue in the above embodiments may be utilized for any number ofdifferent purposes, including for example mobility management ordetermining the geographic position of the device 36. In this lattercase, a reference signal 46 herein will be specifically designed (e.g.,with good signal quality) to be a signal on which a wireless device 36performs positioning measurements. These positioning measurements are tobe used by the device 36 itself, or some server 46 in the core network34 (e.g., a positioning node), for determining the device's geographicposition. In some embodiments, for example, such positioningmeasurements comprise timing measurements. In such a case, a wirelessdevice 36 may measure timing differences (e.g., RSTD or Rx-TX) betweendifferent reference signals 44 received from different cells 42. Thesetiming differences are then used to estimate the device's position withrespect to the different cells 42. Of course, the above embodiments mayemploy any number of positioning method types besides those examplesgiven above. Thus, positioning measurements as used herein may refer toRSTD measurements for OTDOA, RX-TX time difference measurements, timingadvance measurements, received signal strength measurements, receivedsignal quality measurements, or the like.

Still further, those skilled in the art will understand that the abovementioned reference signals 44 for which measurement gaps are configuredare transmitted on non-serving frequencies. In this regard, the signalsmay be inter-frequency measurements, inter-RAT measurements, orinter-band measurements. The above embodiments may therefore beimplemented by wireless devices 36 that need measurement gaps to performreference signal measurements on non-serving frequencies, as well as bywireless devices 36 that do not need such gaps. Indeed, standardizedoperation of a device 36 may dictate that measurement gaps be configuredfor such measurements, even if the device 36 is technically capable ofperforming the measurements without them. One such device 36 may be, forinstance, a device capable of carrier aggregation.

Those skilled in the art will further appreciate that the wirelessdevice 36 described herein may be any wireless node capable ofperforming measurements of reference signals 44 on non-servingfrequencies. In this regard, the wireless device 36 may be a mobileterminal (e.g., a smart phone, a personal digital assistant, a laptop,etc.), a sensor, a mobile relay, or even a small base station or fixedrelay that performs reference signal measurements (e.g., for positioningat setup). In LTE embodiments where the measurements are utilized forpositioning, for instance, the wireless device 36 comprises any LCStarget.

Moreover, the above embodiments have not been described in the contextof any particular type of wireless communication system (i.e., RAT). Inthis regard, no particular communication interface standard is necessaryfor practicing the present invention. That is, the wirelesscommunication system 30 may be any one of a number of standardizedsystem implementations in which a device 36 can perform reference signalmeasurements.

Nonetheless, as one particular example, the system 30 may implement LTEor LTE-based standards. In the context of positioning embodiments,therefore, the server 46 may comprise a positioning node that implementsa positioning platform. If the platform is implemented in the userplane, the server 46 is an SLP node, and if the platform is implementedin the control plane, the server 46 is an E-SMLC node. Moreover,signaling of the positioning result between an E-SMLC node and an LCSClient may be transferred via multiple nodes (e.g., via MME and GMLC).Note also that LTE FDD and LTE TDD are considered as different RATs, andtwo LTE networks are also considered as two different LTE RATs. Finally,reference signals 44 as referred to above may comprise PositioningReference Signals (PRS) in LTE positioning embodiments.

At least in this case, the bandwidth over which PRS are transmitted(i.e., PRS transmission bandwidth) and/or measured (i.e., PRSmeasurement bandwidth) may be made available either in a radio node inthe RAN 32, a positioning node 46 in the CN 34, or another network node(e.g., O&M or SON), and then communicated between the nodes directly orvia other nodes (e.g., eNodeB may communicate with positioning node viaO&M). The communication may also be between eNodeBs, e.g., over X2. Thecommunication comprises at least PRS transmission bandwidth and/or PRSmeasurement bandwidth and/or other PRS information (e.g., anycombination of: muting information, number of subframes, PRSperiodicity, PRS offset from SFN0, or e.g. pico PRS subframe offset froma macro cell in the area).

Of course, those skilled in the art will appreciate that the various“circuits” described may refer to a combination of analog and digitalcircuits, and/or one or more processors configured with software storedin memory 54 and/or firmware stored in memory 54 that, when executed bythe one or more processors, perform as described above. One or more ofthese processors, as well as the other digital hardware, may be includedin a single application-specific integrated circuit (ASIC), or severalprocessors and various digital hardware may be distributed among severalseparate components, whether individually packaged or assembled into asystem-on-a-chip (SoC).

In view of the above modifications and variations, those skilled in theart will appreciate that the radio network node 50 described hereingenerally performs the processing shown in FIG. 5 for configuringmeasurement gaps during which a wireless device 36 is to performmeasurements of one or more neighbor cells 42 on one or more non-servingfrequencies. As shown in FIG. 5, processing includes obtaininginformation that identifies, for each of a plurality of candidatenon-serving frequencies, one or more measurement bandwidths over whichone or more corresponding measurements on that non-serving frequency areto be performed (Block 100). Processing further entails selecting asubset of the candidate non-serving frequencies based on thosemeasurement bandwidths. (Block 110). Finally, processing includesconfiguring measurement gaps during which the wireless device 36 is toperform one or more measurements on the selected non-serving frequencies(Block 120).

Those skilled in the art will nonetheless recognize that the presentinvention may be carried out in other ways than those specifically setforth herein without departing from essential characteristics of theinvention. The present embodiments are thus to be considered in allrespects as illustrative and not restrictive, and all changes comingwithin the meaning and equivalency range of the appended claims areintended to be embraced therein.

What is claimed is:
 1. A method of configuring measurement gaps duringwhich a wireless device is to perform one or more measurements of one ormore neighbor cells on one or more non-serving frequencies, the methodcomprising: receiving, from the wireless device, a request to configureone or more measurement gaps corresponding to one or more candidatenon-serving frequencies; obtaining information that identifies, for eachof the one or more candidate non-serving frequencies, one or moremeasurement bandwidths over which one or more corresponding measurementson that candidate non-serving frequency are to be performed; selecting,based on the information, a subset of the one or more candidatenon-serving frequencies on which one or more measurements are to beperformed; and configuring one or more measurement gaps during which thewireless device is to perform the one or more measurements on theselected subset of the one or more candidate non-serving frequencies. 2.The method of claim 1, wherein: the wireless device is configured toreceive or measure signals from a serving cell over a serving-cellbandwidth; the selecting comprises selecting the subset based on the oneor more measurement bandwidths in relation to the serving-cellbandwidth.
 3. The method of claim 2, wherein the selecting comprisespreferentially selecting, for inclusion in the subset, one or morecandidate non-serving frequencies on which the most neighbor cells areto be measured over a measurement bandwidth that does not exceed adefined threshold set based on the serving-cell bandwidth.
 4. The methodof claim 3, wherein the defined threshold is set to be larger than theserving-cell bandwidth.
 5. The method of claim 2, wherein the selectingcomprises preferentially selecting, for inclusion in the subset, one ormore candidate non-serving frequencies on which the most neighbor cellsare to be measured over a bandwidth equal to the serving-cell bandwidth.6. The method of claim 1, wherein: the wireless device is configured toreceive or measure signals from a serving cell on a serving-cellfrequency over a serving-cell bandwidth, and measurements on a referencecell serve as a reference for the measurements; and wherein selectingthe subset is further based on determining whether the reference cell ison the serving-cell frequency.
 7. The method of claim 1, wherein theselecting comprises preferentially selecting, for inclusion in thesubset, one or more candidate non-serving frequencies on which the mostneighbor cells are to be measured over a measurement bandwidth that doesnot exceed a defined maximum bandwidth.
 8. The method of claim 1,wherein the selecting comprises: determining a majority measurementbandwidth for each candidate non-serving frequency, wherein the majoritymeasurement bandwidth for a given candidate non-serving frequency is themeasurement bandwidth over which the majority of measurements on thatnon-serving frequency are to be performed; and preferentially selecting,for inclusion in the subset, one or more candidate non-servingfrequencies that have a greatest majority measurement bandwidth.
 9. Themethod of claim 1, wherein the selecting and configuring are performedresponsive to determining that measurement gaps cannot be configuredusing a single measurement gap pattern for performing measurements onall of the one or more candidate non-serving frequencies.
 10. The methodof claim 1, wherein the request includes at least part of theinformation, and wherein obtaining the information comprises obtainingat least part of the information via the request.
 11. The method ofclaim 1, wherein obtaining the information comprises: transmitting, to anetwork node, an information request message requesting at least part ofthe information; and receiving, responsive to the information requestmessage, at least part of the information.
 12. The method of claim 1,wherein obtaining the information comprises receiving at least part ofthe information from one or both of the wireless device and a networknode.
 13. The method of claim 1, further comprising obtaining timinginformation regarding when one or more cells corresponding to the one ormore candidate non serving frequencies are to transmit one or morereference signals to be measured during the one or more measurementgaps, wherein selecting the subset is further based on the timinginformation.
 14. The method of claim 13, wherein the timing informationcomprises one or both of timing offset information and mutinginformation corresponding to the one or more cells.
 15. The method ofclaim 1, wherein the one or more measurements comprise positioningmeasurements that are to be used for determining the geographic positionof the wireless device.
 16. The method of claim 15, wherein: the methodis implemented in a Long Term Evolution (LTE) network; and thepositioning measurements are performed on Positioning Reference Signals(PRS).
 17. The method of claim 15, wherein the positioning measurementscomprise any one or more of: Reference Signal Time Difference (RSTD)measurements for Observed Time Difference of Arrival (OTDOA),Receive-Transmit (Rx-Tx) time difference measurements, Timing Advance(TA) measurements, received signal strength measurements, and receivedsignal quality measurements.
 18. The method of claim 1: wherein the oneor more measurements comprise one or more of: intra-frequencymeasurements, inter-frequency measurements, intra-RAT measurements,inter-RAT measurements; and wherein an inter-frequency or inter-RATmeasurement comprises either an intra-band measurement or an inter-bandmeasurement.
 19. The method of claim 1, wherein the wireless devicerequires measurement gaps in order to perform the one or moremeasurements on the one or more non-serving frequencies.
 20. The methodof claim 1, wherein: the method further comprises configuring ameasurement pattern for the wireless device to perform the one or moremeasurements; and the measurement pattern indicates low-interferencesubframes in which the wireless device is to perform the one or moremeasurements.
 21. A radio network node for configuring measurement gapsduring which a wireless device is to perform one or more measurements ofone or more neighbor cells on one or more non-serving frequencies, theradio network node comprising: a communications interface configured toreceive, from the wireless device, a request to configure one or moremeasurement gaps corresponding to one or more candidate non-servingfrequencies; and one or more processing circuits operatively connectedto the communications interface, wherein the one or more processingcircuits are configured to cause the network node to: obtain informationthat identifies, for each of the one or more candidate non-servingfrequencies, one or more measurement bandwidths over which one or morecorresponding measurements on that candidate non-serving frequency areto be performed; select, based on the information, a subset of the oneor more candidate non-serving frequencies on which one or moremeasurements are to be performed; and configure one or more measurementgaps during which the wireless device is to perform the one or moremeasurements on the selected subset of the one or more candidatenon-serving frequencies.